The present invention relates to conformable molds of hydrogel which are adapted for the casting of polyelectrolytic materials. The present invention also relates generally to the articles formed thereby, and specifically, to transparent contact lenses.
Hydrogel materials comprising hydrophilic polymers are well known to the prior art. These hydrogels are capable of absorbing ionic substances from aqueous solutions when the hydrogel is hydrated or equilibrated in such solutions. The speed of absorption, degree of swelling upon hydration, hardness and flexibility are capable of being tailored to yield precise physical properties. The ability to alter or otherwise predict these physical properties rests, primarily, upon the chemical composition of the hydrogel and, to a lesser degree, upon the aqueous ionic solution employed for hydration or equilibration. When the hydrogel is hydrated with such ionic aqueous solutions, controlled delivery of the ionic species therefrom is readily achieved.
Polyelectrolytic materials are similarly known in the prior art, and are characterized as possessing active charged sites termed polarites. When certain polyelectrolytic materials are contacted by ionic species, they will gel or congeal into a self-sustaining mass, rather than form a flocculent precipitate, upon proper control of the chemical environment. Examples of naturally occuring products exhibiting these characteristics are various polysaccharides including gelatins, alginates, etc. Additionally, synthetic materials such as sodium acrylate, complexes of acrylic acid, styrene, and copolymeric reaction products of sulfonic acid similarly are capable of gelling or congealing upon treatment with specific ionic species.